Field of the Invention
The present invention relates to a developing device used in an electrophotographic image forming apparatus that forms an image on a recording medium through an electrophotographic image forming method, and a process cartridge and an image forming apparatus that include the developing device.
Description of the Related Art
Conventionally, the following developing device has been widely used in an image forming apparatus. More specifically, a developing roller bears developer on its circumferential surface and rotates to supply the developer to an electrophotographic photosensitive member arranged to face the developing roller, so that an electrostatic latent image formed on the electrophotographic photosensitive member is developed.
Further, a developer agitation member for agitating the developer stored in a developer container is used in the developing device. As illustrated in FIG. 11, there has been known a developer agitation member 23 that includes a plurality of rotational agitation portions 23a1 to 23d1 having different rotation radii and being supported by respective supporting portions 23a2 to 23d2 of a shaft portion 23e serving as a rotation center of the entirety (Japanese Patent Application Laid-Open No. 2006-99044).
The developer agitation member 23 is configured in such a manner that distances from the shaft portion 23e serving as a rotation center of the entirety to the supporting portions 23a2 and 23c2 respectively supporting the rotational agitation portions 23a1 and 23c1 are set longer than distances from the shaft portion 23e to the supporting portions 23b2 and 23d2 respectively supporting the rotational agitation portions 23b1 and 23d1. With this configuration, loci of the rotational agitation portions 23a1 and 23c1 rotating about the shaft portion 23e are set to be larger than loci of the rotational agitation portions 23b1 and 23d1 rotating about the shaft portion 23e. Further, coil-shaped movable agitation portions 23a4 to 23d4 having the inner diameters larger than the outer diameters of the rotational agitation portions 23a1 to 23d1 are movably attached to the outer circumferences of the respective rotational agitation portions 23a1 to 23d1.
Then, when the developer agitation member 23 is rotated, developer within a developer container 24 can be scooped up and agitated, so that the developer within the developer container 24 and the developer newly supplied to the developer container 24 can be sufficiently agitated and then supplied to a developing roller.
However, the above-described conventional technique has limitations in terms of design because the configuration thereof requires a large number of components. Therefore, although there is a demand for a miniaturized and low-cost image forming apparatus, it is difficult to satisfy such a demand for lower cost.